A federal judge has struck down the state's voter-approved rules toughening standards for revoking paroles, saying they violate the right to legal representation and tilt the system in favor of sending ex-cons back to prison.

The procedures were part of Proposition 9, passed by a 54 percent majority in November 2008, and affecting revocation hearings for tens of thousands of parolees accused each year of violating the terms of their release.

Prop. 9 did not guarantee parolees the right to present evidence at the hearings. It also allowed parole agents to testify about incriminating statements by witnesses who were not in court, and required the state to provide lawyers only for parolees who appeared unable to defend themselves.

Another provision required the parole board to consider "the safety of victims and the public" but to disregard the costs and burdens of imprisonment when deciding whether to revoke parole.

Court challenges, in a suit initially filed by parolees against an earlier set of rules in 1994, have prevented the new procedures from taking effect. U.S. District Judge Lawrence Karlton of Sacramento had struck down the provisions on evidence and legal representation in 2009, saying they violated an order he had issued five years earlier to protect parolees' rights.

Told by a federal appeals court to reconsider the case under constitutional standards, Karlton ruled Tuesday that all of Prop. 9's provisions for parole revocation were invalid.

In particular, he said, the requirement to consider only public safety, and disregard the costs and burdens of imprisonment, "violates parolees' right to a neutral decision-maker by placing a thumb on the scale of justice and tipping the balance towards incarceration."

The U.S. Supreme Court has ruled that parolees have a right to present evidence at revocation hearings and question all opposing witnesses, unless the state has a legitimate reason to keep a witness out of court, Karlton said. And he reaffirmed his previous ruling that parolees are entitled to lawyers at the hearings.

The ruling doesn't affect other sections of Prop. 9, which require prisoners serving life terms to wait as long as 15 years between parole eligibility hearings and expand the rights of crime victims and their families to take part in parole proceedings.

Ernest Galvan, a lawyer for the parolees, said Thursday the ruling promotes fairness without endangering the public.

"When you cut back on the fairness of the hearing process, you're hurting public safety by locking up people without being sure whether they're even the right people or whether they're dangerous," he said.

State prison officials were reviewing the ruling, said spokesman Luis Patino.